Workstring Disconnect Tool and Method of Use

ABSTRACT

A tool for economically, efficiently, and reliably separating a workstring in a wellbore is disclosed.

FIELD OF THE INVENTION

The invention pertains to tools for allowing rapid and economicaldisconnection of a workstring in a wellbore.

BACKGROUND OF THE INVENTION

Drilling technology has evolved allowing wells to be drilleddirectionally so that larger portions of the wellbore can reside withinthe hydrocarbon bearing deposit, thus increasing productivity. Wells areincreasingly being directionally drilled. Directional drillingintroduces new challenges, including sticking of the workstring.

When the workstring lies on the low side of a directional well bore andthe well is in an overbalanced pressure state, the workstring oftenbecomes differentially stuck. The method for fishing a stuck workstringrequires releasing of the workstring above the point of sticking andrunning back in with a fishing tool assembly in order to jar the stuckworkstring free.

Conventional methods of releasing from and reconnecting the workstringare time consuming and costly. It is desirable to provide an efficientand cost-effective device and method for releasing a workstring “above”(that is, nearer to the surface) a stuck portion of a workstring,returning to efficiently re-couple to the stuck workstring portion witha fishing tool, for example, ajar, and proceeding with drillingoperations once the stuck portion of the workstring has been freed.

SUMMARY OF THE INVENTION

The invention is a disconnect tool for separating portions of aworkstring in a wellbore. If a workstring becomes stuck, it is necessaryto “unlink” the portion of the workstring above the stuck section, so itcan be removed from the wellbore and a fishing tool, such as a jar, canbe run downhole to attempt to free the stuck section of workstring.(Those of skill in the art will recognize that terms such as “above” and“up” are understood to mean “closer to the surface,” and that “below”and “down” mean “further from the surface.” These conventions arenecessary because, with the use of directional drilling techniques, theaffected portion of the workstring may be horizontal, or nearly so.)

The tool comprises an upper body, a lower body, and a ball seat sub thatcan be shifted from a first (initial) position to a second position. Inthe first position, the ball seat sub maintains a mechanical linkage(such as, for example, by the use of intermeshed splines) with the upperbody and with the lower body, so that the upper body, ball seat sub, andlower body are rotationally locked together. Thus, with the ball seatsub in the first position, the disconnect tool acts simply as anotherlink in the workstring.

Should the portion of the workstring below the disconnect tool becomestuck, the disconnect tool can be utilized to separate the upper bodyand the portion of the workstring above the disconnect tool from thelower body and the stuck portion of the workstring. This action isaccomplished by dropping or pumping a shifting ball down the workstringto seat on the ball seat of the ball seat sub. Hydraulic pressure isthen used to release a retaining device, such as by shearing shearscrews or pins, and allowing the ball seat sub to shift down relative tothe upper body, releasing the mechanical linkage between the upper bodyand the ball seat sub.

With the ball seat sub in this second position, the upper body and theball seat sub (and, thus, the lower body) are no longer rotationallylocked. In a preferred embodiment of the invention, the linkage betweenthe upper body and the lower body is a left-handed threaded connection,so that continued normal (clockwise) rotation of the workstring willseparate the upper body from the lower body. Once separated, the upperbody and the portion of the workstring above it can be withdrawn fromthe wellbore.

Additionally, in a preferred embodiment of the invention, the lower bodyis provided with a right-handed thread external retrieval thread, sothat an appropriate retrieval tool may be run downhole and threaded ontothe lower body to begin retrieval operations. The retrieval tool may beintegrated with, or merely attached to, a fishing tool, such as a jar orother device. Upon completion of fishing operations, the intactworkstring may be removed from the wellbore or used to continue downholeoperations.

Those of skill in the art will recognize that multiple workstringdisconnect tools of the present invention can be spaced at variouslocations in the workstring, and may, for example, be provided withvariously sized ball seats. In this way, the operator may have a choiceof which of the tools to use to separate the workstring, thus allowing achoice of where along the workstring the separation will occur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross sectional view of a workstring disconnect toolof the present invention configured to run in to a wellbore.

FIG. 2 is a partial cross sectional view of a retrieving sub for usewith the present invention.

FIG. 3 is a partial cross sectional view of a workstring disconnect toolof FIG. 1, with a shifting ball in its initial position.

FIG. 4 is a partial cross sectional view of a workstring disconnect toolof FIG. 1 in the releasing position.

FIG. 5 is a partial cross sectional view of a workstring disconnect toolof FIG. 1 after completion of the releasing operation.

FIG. 6 is a partial cross sectional view of the lower body of aworkstring disconnect tool of FIG. 1 with a retrieving sub (FIG. 2)ready to be engaged.

FIG. 7 is a partial cross sectional view of the lower body of aworkstring disconnect tool of FIG. 1 in sealing engagement andmechanical linkage with a retrieving sub (FIG. 2).

FIG. 8 is a partial cross sectional view of the upper body of aworkstring disconnect tool of FIG. 1.

FIG. 9 is a side view of a ball seat sub of the present invention.

DETAILED DESCRIPTION

Referring to FIG. 1, a workstring disconnect tool 10 of the presentinvention is shown in its run-in configuration. Workstring disconnecttool 10 comprises workstring coupler 14, upper body 12, ball seat sub70, and lower body 42. Upper body 12 and lower body 42 are connected bythe intermeshing of upper body internal thread 22 and lower bodyexternal thread 46. This threaded relationship is preferably lefthanded, so that when the internal interlock of the workstring disconnecttool 10 is disengaged as described below, continued normal rotation ofthe workstring will separate upper body 12 and lower body 42.

Referring also to FIG. 9, sealing between the upper body 12 and the ballseat sub 70 is provided by upper ball seat seal 30, which is positionedin upper seal groove 72, and lower ball seat seal 32, positioned inlower seal groove 76. Shearable device 40 (such as shear screws or pins)holds ball seat sub 70 in its first position relative to upper body 12,by engagement with shearing spotface 74. Sealing between upper body 12and lower body 42 is provided by the engagement of upper body sealingsurface 20 with connector seal 34.

In the run-in position, upper body internal keyway 18 (see, also, FIG.8), comprising, for example, splines, intermeshes with ball seat subexternal keyway 80 to rotationally lock ball seat sub 70 to upper body12, and thus (via workstring coupler 14) to the portion of theworkstring above the workstring disconnect tool 10. S Similarly, ballseat sub external keyway 80 simultaneously intermeshes with lower bodyinternal keyway 48, rotationally locking ball seat sub 70 to lower body42.

Referring now to FIGS. 1, 3-5, should the workstring become stuck belowworkstring disconnect tool 10, the tool can be utilized by the followingprocess. Shifting ball 90 is dropped or pumped downhole through theworkstring (not shown) to seat on ball seat 86. Once shifting ball 90 isin sealing engagement with ball seat 86, hydraulic pressure isincreased, shearing shearable device 40, such as shear screws or pins.(Those of skill in the art will recognize that a plurality of shearscrews or shear pins spaced around the circumference of the ball seatsub will be desirable.) The hydraulic pressure then shifts ball seat sub70, placing ball seat sub 70 in its second position. In this position,upper body internal keyway 18 (see, also, FIG. 8) is separated from ballseat sub external keyway 80, so that ball seat sub 70 is no longerrotationally locked to upper body 12.

In this configuration, continued normal (clockwise) rotation of theworkstring, will disengage the left-handed threaded relationship betweenupper body internal thread 22 and lower body external thread 46,separating upper body 12 from lower body 42. The workstring may now bewithdrawn from the wellbore, pulling with it upper body 12, ball seatsub 70, and shifting ball 90. Lower body 42 and the continuation of theworkstring (not shown) connected to lower body 42 at lower workstringconnection 56 remain in the wellbore, awaiting rescue. As the workstringis withdrawn, drain holes 16 allow the outflow of well fluid from theinterior of the workstring.

Referring now to FIGS. 6 and 7, the connection of a retrieval tool 60 tolower body 42 is shown. Retrieval tool 60 comprises an internalretrieval thread 66 for engagement with external retrieval thread 52 onlower body 42. Retrieval tool 60 may be any type of, or (as is morelikely the case) may be coupled to (via retrieval tool coupler 62), anytype of tool, such as, for example, a jar, designed to recover a stucktoolstring.

As retrieval tool 60 is positioned relative to lower body 42, lower endguide 68 assists in correct alignment. As internal retrieval thread 66engages external retrieval thread 52 on lower body 42, the normal(clockwise) rotation of the workstring will tighten the threadstogether, until torque shoulder 64 engages lower body upper end 44, andretrieval tool seal 36 is in sealing engagement with lower body sealingsurface 54.

Those of skill in the art will understand that the descriptions aboveare by way of example only, and that variations on the above can be madewithout departing from the spirit of the invention.

We claim:
 1. A disconnect tool for separating a workstring in a wellbore, comprising an upper body, a lower body, selectively connectable tosaid upper body, and a ball seat sub, selectively movable from a firstposition to a second position, wherein in said first position, said ballseat sub is rotationally locked to both said upper body and said lowerbody, and in said second position said ball seat sub is not rotationallylocked to said upper body.
 2. The disconnect tool of claim 1, whereinthe selective connection between said upper body and said lower body isa left-handed threaded connection.
 3. The disconnect tool of claim 1,wherein said ball seat sub is selectively movable by use of hydraulicpressure.
 4. The disconnect tool of claim 1, wherein said lower bodyadditionally comprises a retrieval connection.
 5. The disconnect tool ofclaim 4, wherein said retrieval connection is a sealable connection. 6.The disconnect tool of claim 4, wherein said lower body said retrievalconnection is an exterior, right-handed threaded connection on saidlower body.
 7. The disconnect tool of claim 1, wherein said ball seatsub is retained in said first position by a plurality of shearabledevices.
 8. The disconnect tool of claim 7, wherein said shearabledevices are shear screws.
 9. The disconnect tool of claim 7, whereinsaid shearable devices are shear pins.
 10. A method of disconnectingportions of a workstring in a wellbore, comprising providing as part ofthe workstring a disconnect tool comprising an upper body, a lower body,and a ball seat sub, wherein said ball seat sub maintains a rotationallock to said upper body and said lower body, and wherein said upper bodyand said lower body are selectively connected, shifting said ball seatsub so that it is not rotationally locked to said upper body, anddisconnecting said upper body from said lower body.
 11. The method ofclaim 10, additionally comprising the step of providing a left-handedthreaded connection as the selective connection between said upper bodyand said lower body.
 12. The method of claim 10, additionally comprisingthe step of providing said lower body with a selective connection for aretrieval tool.
 13. The method of claim 10, wherein the step ofproviding said lower body with a selective connection for a retrievaltool additionally comprises the step of providing a right handedthreaded connection on said lower body.
 14. The method of claim 10,additionally comprising the step of providing a sealable connection fora retrieval tool on said lower body.
 15. The method of claim 12,additionally comprising the step of providing a sealable connection fora retrieval tool on said lower body.
 16. The method of claim 14,additionally comprising the step of continuing well operations withoutremoving the workstring from the wellbore.
 17. The method of claim 15,additionally comprising the step of continuing well operations withoutremoving the workstring from the wellbore.